UFH questions.

Bendy_House

A few Qs about mil's UFH, please.

1) I'm guessing, by the way they work sloooowwwlllyyy - that these are wax-controlled valves? So have little electric heaters inside them? Or how else do they work? (Just curious). We also had one zone - a bedroom - come on to a very warm temp, over 21oC, even tho' the wall stat was turned right down. I had assumed that I'd find motorised valves controlling the zones, but found these babies instead. Q - I tested them by turning wall stats up and down, and they seem to work fine, including the one that was seemingly 'on' when it shouldn't be. Can these 'stick' intermittently like motorised valves can? Any explanation why a zone would be on when it shouldn't be? (Other than, cough, user error - always a possibility)?

2) Are these - yellow-circled - auto air valves? Is it ok for me to try opening the wee red caps to see if there's any more air in there? The 'valves' hisssss when in part-open mode - is this normal?

Thanks.

tacpot12

You are correct. They have wax motors in them which means they take 3-5 minutes to open fully (the little electric heaters in them cause the wax to expand) . If you want a better solution, have a look at the  Salus Auto Balancing Actuators. These have an electric motor in them, and open mum more quickly, plus they balance each underfloor heating zone for the correct 7 degree delta-T. 

One or two people have problems with the Sulus Actuators, so I would only buy one to start with and then buy more if you find they work well for you.

The wax motors actuators are very reliable, so I suspect there is something else going on to cause the one bedroom to come on. It's more likely that the valve under the actuator has become jammed open. If you were to swap two thermostats over, and the problem moves with the 'stat, you know that it's the stat that is the problem. Similarly, you could swap two actuators over and see if the problem moves with the actuator. If you think it is the valve, you can apply some WD40 to the pin, and pull it up with some pliers or gently tap it with a hammer.

Bendy_House

Fab, Tacpot.

Ah, so a bit like TRVs then? Ie, the wax heads will come off, to expose the actual valves underneath? And these will have 'pins'?

Can the heads be removed without affecting any adjustment? If so, I'd be happy to try sili spray on them.

Thanks. And I shall do my research too

Chickereeeee

TRVs usually (always?) jam OFF. (I.e. pin down). I have never known one to jam on, as that means it is resisting the actuator pressure to turn off.

Bendy_House

Good point, Chick - thank you.

I'm suspecting 'user error'!

MIL isn't used to the ~3-hour hysteresis! She may have turned up the bedroom zone, then turned it back down an hour before we turned up and I discovered the floor still warm under my stockinged feet!

daveyjp

The wall stats can also fail and call for heat when they are off.

fenwick458

the wax head come off yes, should just click on/off like in this video.
unless everything is labelled and always has been, it's possible they have been mixed up (or even installed wrong from the start) which could explain why you said one zone was on and the stat was not calling for heat.
try this, one by one call for heat from each of the room stat, and once you've identified which zone it is put a label on on the head.
and the next part might take a few days, turn on one zone at a time at the stat to verify that they are all correct, and once you know they are all correct put labels on the red pipes.

amcc1

Does the 21oC bedroom have an ensuite with towel rail? Is it possible that the bedroom stat is connected to two valves?

amcc1

Sorry, can’t edit the above post. 2nd sentence doesn’t make sense - unless some cross wiring etc.

Bendy_House

daveyjp said:

The wall stats can also fail and call for heat when they are off.

Thanks. I've checked them, and the red indicator lights at the manifold come on and off as expected. She did have three faulty stat replaced as well.

It all seems to be working fine recently.

Bendy_House

fenwick458 said:

the wax head come off yes, should just click on/off like in this video.
unless everything is labelled and always has been, it's possible they have been mixed up (or even installed wrong from the start) which could explain why you said one zone was on and the stat was not calling for heat.
try this, one by one call for heat from each of the room stat, and once you've identified which zone it is put a label on on the head.
and the next part might take a few days, turn on one zone at a time at the stat to verify that they are all correct, and once you know they are all correct put labels on the red pipes.

Thanks, Fen - I'll check that vid out.

Pretty sure they are all correctly plumbed, but will monitor that. Mainly suspect 'user-error' now; mil didn't appreciate the lag in response, being used to normal rads. Very good chance she turned up the bedroom stat, now't happened, turned it up some more, ditto. And then I found the room was super-warm when we visited, despite the stat having been turned back down at some point.